The objective of the proposed project is to explore methods of recognizing allergy-proneness at the earliest feasible age in the perinatal period. Early recognition will be sought through in-vitro study of aliquots of amniotic fluid and umbilical cord blood specimens obtained for other medical indications. Infants will be followed prospectively to determine whether or not allergic symptoms appear. Associations between IgE levels, specific IgE antibody concentrations, B and T cell functions, and histocompatibility types will be sought as they relate to the subsequent appearance of symptoms. IgE levels will be determined by double antibody radioimmunoassay employing radiolabelled IgE (ND) and anti IgE (Fc PS). Specific IgE antibodies will be determined by the radioallergosorbent test (RAST). Lymphocyte responses and histocompatibility typing will be carried out by appropriate microtechniques. The ultimate aim is to find a means by which allergy can be recognized sufficiently early and with sufficient certainty to permit an objective evaluation of preventive management. Only aliquots of amniotic fluid obtained for other medical reasons will be used for the study. If it is shown that infants at high risk for allergy can be identified before or at birth at insignificant risk to the infant, the tests could ultimately be offered on request to prospective parents who have previously been devastated by personal allergy or by severe allergy in earlier offspring.